As one example of a structure of turning a key in a keyboard apparatus, there is a structure where a thin plate having flexibility is arranged horizontally (e.g., PTL 1: Japanese Patent Application Laid-Open No. 2008-191650). By deforming this thin plate, the key can be turned in upward and downward directions. In PTL 1, a structure that by further using another thin plate arranged vertically concurrently and serially connecting the same to the thin plate arranged horizontally, movement in a direction in which keys are arrayed can be allowed is also disclosed.